Add command-line options for specifying a report output file and the type of the report

[vkarak]

Proposed options:

• -F X or --file X for output file
• --report X for specifying the type. Default type should be the standard reframe report, i.e., the summary report produced at the end or a bit augmented to record also the successes. We could then omit completely the reframe.out file and just store the generated report file in the production and maintenance execution modes.

[jgphpc]

Is it done already here:
https://github.com/eth-cscs/reframe/blob/master/reframe/frontend/cli.py#L183 ?

[vkarak]

Indeed, it was addressed by #1377.